Method and apparatus for pressurized product production

Abstract

The present invention relates to a method and apparatus for producing a pressurized product stream product by cryogenic rectification. A main heat exchanger, used in the cryogenic rectification, warms a pumped product stream composed of oxygen-rich or nitrogen-rich liquid and thereby produces the pressurized product stream. Layers of the main heat exchanger are designed such that a reduction in the heat transfer area provided within the main heat exchanger for warming the pumped product stream occurs at a location at which the temperature of the pumped product stream exceeds either the critical or a dew point temperature of such stream. The reduction in heat transfer area leaves regions of the layers able to heat or cool another stream that is used in connection with the cryogenic rectification. Such other stream can be a refrigerant stream that allows the introduction of additional refrigeration to increase production of liquid products.

Description

FIELD OF THE INVENTION [0001]The present invention relates to a method and apparatus for producing a pressurized product stream by cryogenic rectification in which the product stream is formed from a pumped product stream composed of oxygen-rich or nitrogen-rich liquid that is warmed within a main heat exchanger that is used in connection with the cryogenic rectification. Even more particularly, the present invention relates to such a method and apparatus in which the pumped product is warmed within layers of the main heat exchanger that are designed to both warm the pumped liquid product and warm or cool another stream.BACKGROUND OF THE INVENTION [0002]Oxygen is separated from oxygen containing feeds, such as air, through cryogenic rectification. In cryogenic rectification, the feed is compressed, if not obtained in a pressurized state, purified of contaminants and then cooled in a main heat exchanger to a temperature suitable for its rectification. The cooled feed is then introduc...

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Benefits of technology

[0009]It is to be noted although the claims are addressed to a method of producing a pressurized product stream, it is not intended that the present invention be limited to a cryogenic rectification process or plant employing such process in which only a single pressurized product stream is produced in that the method could be applied to produce a nitrogen-rich product stream or an oxygen-rich product stream or both simultaneously. Further, the term, “main heat exchanger” as used herein and in the claims includes one of such units or several of such units connected in parallel. A principle under which the present invention operates is that it takes more heat to warm the pumped liquid oxygen stream to its critical temperature, if a supercritical fluid is the intended or to the dew point temperature if a vapor product is desired then to afterwards warm either of such streams to the warm end temperature of the main heat exchanger. In the prior art, however, the layers within the main heat exchanger that are used for warming the pumped liquid oxygen stream are designed to warm subsidiary streams thereof from entering the cold end temperature of the pumped liquid oxygen stream to the warm end temperature of the main heat exchanger. Consequently, not all of the heat transfer area provided by the layers in such a prior art heat exchanger are being efficiently used because there is less heat transfer duty in warming the subsidiary streams from the critical temperature or dew point temperature to ambient. In the present invention, however, once the critical temperature or dew point temperature is exceeded, the subsidiary streams are combined leaving regions within the layers available for heating or cooling another stream. In such manner, the main heat exchanger can be fabricated in a more compact manner than in the prior art, resulting in substantial savings in the acquisition costs of such heat exchanger. Moreover, as will be discussed, there are other advantageous operations that are made available by such arrangement in connection with the production of liquid products.

Problems solved by technology

In any event, the cost of such heat exchangers represents a major cost of the cryogenic rectification plant and typically, the price of a particular heat exchanger is based upon its volume.

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